I installed a pull switch on a whole house fan that was originally 2 speeds and now I’m getting 3 speeds. It appears it is feeding both sets of windings versus just each set individually on the 3rd speed. Is this going to be a problem?
I’m curious about this as well, if only from the standpoint of an idle observer.
This is not nearly as exciting as an “electrical whore house fan motor question,” which is what I originally mistook it for.
When you say it appears to be feeding both sets of windings do you mean it’s going slower than before on one speed? It might not be able to cool itself if running slower on hot days.
Look at the motor’s wiring diagram. It’s usually right on the nameplate. If not, get the make / model and post it, and I’ll try to look up the correct wiring.
I took the original switch apart. it is a single input feeding 2 lines one at a time. It could only work by feeding 1 set of windings and then another. There are only 2 input leads (plus ground) on the motor. What the new switch appears to do is feed the first set of windings, then both, and then the 2nd set of windings (thus giving 3 speeds). the result is medium speed, then high speed, and then low speed (the order could be reversed). Is this how 3 speed motors are usually set up or are they always 3 sets of windings?
If both windings in give you the highest speed then they are in parallel. The only concern I would have is that you aren’t suddenly drawing more than the breaker was selected for.
I’m guessing that your new switch is not correct for this motor, and you might overheat it. Take a look at this: http://www.butcherdistributors.com/Images/Interior/motor%20catalog.pdf
There is a lot of motor info here.
Sigh… After looking at switches for an hour there are clearly ones designed to feed both circuits as a 3rd speed. What part of 2-speed switch did the person I bought it from not understand.
I’d say this is when you either put the old switch back or hire an expensive licensed electrican to check out your install. 
It’s operationally fine, it’s just a matter of whether the motor will handle the heat of running both windings at the same time. I’s a more efficient way of making a 3 speed motor. I’m going to swap a true 2-way in when I get the chance. There’s nothing to be gained by a higher speed on a whole-house fan unless you want to suck the fir directly off your pets.